1. Field of the Invention
The present invention relates to a disposable intraluminal ultrasonic instrument which includes a catheter that has a sound wave transducer therein and a rotatable acoustic mirror for directing the sound waves outwardly into tissue and for receiving echo sounds and directing the echo sounds to the transducer for transmission to a visual display which displays an ultrasound picture of the tissue whereby one can determine the makeup or constitution of the tissue, e.g., hard or soft. More particularly, the present invention relates to such an instrument wherein the catheter tip is not greater than 3 millimeters in diameter and has mounted therein a very small electric motor for rotating the acoustic mirror while the transducer provides sound waves to the acoustic mirror at a frequency no greater than 60 megahertz.
2. Description of the related art including information disclosed under 37 CFR Sections 1.97-1.99.
Heretofore it has been proposed in Dutch Patent Application No. 87.00632 to provide a catheter having a catheter tip with a rotatable acoustic mirror therein or a rotatable tip having an acoustic mirror therein. A flexible shaft extends from the rotatable acoustic mirror to the proximal end of the catheter where it is driven by a suitable motor situated outside the catheter. A transducer is mounted in the catheter tip opposite the rotatable acoustic mirror. Rotation of the acoustic mirror within the tip or the tip portion having the mirror thereon causes high frequency ultrasonic vibrations or sound waves emitted by the transducer to be emitted in different directions in a rotating path and the echoes of the sound waves are received by the acoustic mirror and thence by the transducer for transmission to a visual display whereby a picture can be created of the space around the catheter tip which may contain tissue or a stenotic buildup in a vessel.
A problem with the instrument having the catheter described above is that the flexible drive shaft is fairly long, i.e., at least as long as the catheter itself. With this arrangement, it is difficult to supply a torsion free rotational force through the flexible drive shaft and to drive such a long flexible drive shaft for extended periods of time without malfunctioning.
As will be described in greater detail below, the present invention provides an intra-luminal ultrasonic instrument which does not have the problem of a long drive shaft by providing a small motor in the catheter tip for driving a short drive shaft coupled to an acoustic mirror in the catheter tip.
It has been suggested in Dutch Patent Application No. 87.00632 to provide a turbine driven by fluid at or near the catheter tip with the turbine having a short drive shaft coupled to the rotatable acoustic mirror.
Heretofore it has been proposed in European Patent Application Publication No. 0 139 574 to provide an endocavity probe having a motor mounted in the distal end of one embodiment of the probe. The motor rotates a mirror which reflects signals emitted by a transducer.
This probe is utilized in examining organs and the like of a body. The probe is somewhat bulky in shape and size, is intended for insertion in body cavities, is not suitable for insertion inside veins and/or arteries and does not teach a motor having a diameter no greater than 3 millimeters in a catheter tip.
In the Sakai German Offenlegungsschrift DE 32 19 118 A1 there is disclosed an endoscope having a metal housing in which is mounted a rotatable mirror and a motor for rotating the mirror. Also fiber optics are provided for viewing capabilities. This patent publication does not disclose or suggest a catheter tip no greater than 3 millimeters in diameter having a motor mounted therein for rotating an acoustic mirror positioned adjacent to a transducer in the catheter tip.
The Eggleton et al. U.S. Pat. No. 4,546,771 discloses an acoustic microscope which has a transducer capable of producing and receiving high frequency acoustical beams and is positioned within a needle. This patent teaches using frequencies of 100 megahertz to 400 megahertz, and preferably frequencies of 500 megahertz or greater. These frequencies do not produce the necessary depth obtained with frequencies under 60 megahertz as utilized in the intra-luminal ultrasonic instrument of the present invention.
This patent teaches the rotation of a rotating member by an arrangement of small electromagnets and permanent magnets attached to a needle. The needle in this patent can only be inserted into tissue for biopsy procedures and is not adapted to be inserted into a blood vessel, nor is it intended to be inserted into a blood vessel like the catheter tip of the present invention for evaluating space around the catheter tip and particularly, the tissue or stenotic buildup located around the catheter tip to a sufficient depth.